**Core Concept**
The patient's presentation of increasing RUQ pain, a mass in the RUQ, elevated liver enzymes (AST and ALT), and an elevated alpha-fetoprotein (AFP) level, in the context of a prior history of hepatitis B, suggests a diagnosis of hepatocellular carcinoma (HCC). HCC is a type of primary liver cancer that is strongly associated with chronic hepatitis B infection, which is a common cause of liver cancer worldwide.

**Why the Correct Answer is Right**
The patient's HBsAg-positive, HBsAb-negative status indicates chronic hepatitis B infection, which is a major risk factor for HCC. The elevated AFP level is a tumor marker commonly used to diagnose HCC. Additionally, the presence of a mass in the RUQ, coupled with the patient's liver enzyme abnormalities, suggests a focal lesion within the liver. HCC typically presents as a single, large mass within the liver, which is consistent with the patient's presentation. The lack of significant weight loss, abdominal distension, or other systemic symptoms also supports the diagnosis of HCC, as these are more typical of advanced liver disease.

**Why Each Wrong Option is Incorrect**
**Option A:** A hepatoma is an older term for HCC, but it is not a preferred term in modern medical literature, as it can be confusing and does not accurately reflect the histopathological characteristics of the tumor.

**Option C:** Metastatic cancer to the liver is a possibility, but the patient's elevated AFP level and the presence of a mass in the RUQ are more suggestive of a primary liver tumor, such as HCC, rather than metastatic disease.

**Option D:** Hepatic hemangioma is a benign vascular tumor of the liver that is often asymptomatic and discovered incidentally on imaging studies. The patient's clinical presentation and laboratory findings are not consistent with a diagnosis of hepatic hemangioma.

**Clinical Pearl / High-Yield Fact**
It is essential to note that chronic hepatitis B infection is a major risk factor for HCC, and patients with a history of hepatitis B should undergo regular screening for liver cancer, including AFP levels and abdominal imaging.

**✓ Correct Answer: B. hepatocellular carcinoma (HCC)**